Plating Method and Apparatus, and Strip Obtained by this Method

ABSTRACT

A method for plating strips including providing a strip of material, providing a masking belt including patterned windows, providing a tank with a plating solution, generating a continuous movement in the cell of an assembly of the strip and masking belt, whereby the structure of the masking belt masks portions of the strip in the tank.

FIELD OF THE INVENTION

The instant invention relates to plating methods and apparatus for theplating of strips. For instance, the plating method and apparatus isapplicable to the manufacture of electrical terminals and electricalconnectors, and strips obtained by these methods.

BACKGROUND OF THE INVENTION

In this document the invention is described in relation to themanufacturing of electrical terminals for connectors used in automotiveor telecommunication applications, but as it will be understood from thefollowing the invention can be used for plating any kind of strip ofmaterial and in particular flexible metal strips.

In the application chosen for illustrating the invention strips to beplated are connector terminal strips. One may use rigid structures suchas so-called “lead frames” or “carriers” for supporting these electricalterminals. A lead frame or carrier enables to hold together theterminals during their manufacturing process, which makes a continuousmanufacturing process possible on an industrial scale. At a final stageof the manufacture process of the connector, the terminals are separatedaway from the frame or carrier, which is scraped.

One of the steps of the manufacture of electrical terminals is theplating of a metallic conductor such as, for example gold, on theirsurface. The strip of lead frames or carriers is continuously moved inan electroplating cell between two independent belt portions, which areused to carry the lead frames or carriers. There is a need to make thisprocess more efficient.

In the following, for the sake of simplification, the word “carrier” isused for designating either a lead- frame or any other kind of carrier.

SUMMARY OF THE INVENTION

The invention relates to a method for the manufacture of plated strips.

This method comprises the provision of a strip, for instance a metallicstrip. This strip comprises a top band, a bottom band, a structurejoining together the top and bottom bands, and leads disposed betweenthe top band and the bottom band. For instance, these leads are designedto form electrical terminals for electrical connectors.

A masking belt is provided. The belt comprises a top band, a bottomband, and a structure joining together the top and bottom bands.

A tank is provided. For instance this tank is a metallisation cell witha chamber receiving a solution of an electrical conductor, and anelectrode.

A continuous movement of an assembly of the strip and the masking beltis generated in the cell. The masking belt masks at least partially thestrip in the cell.

The electrical conductor is electroplated on the metallic strip in thesolution by applying an electrical field between the strip and theelectrode during the continuous movement. The electroplating occurs onlyon the uncovered or unmasked portions of the strip.

With these features, no electrical conductor is applied on the maskedportion of the strip. Since this portion may be scraped and/or not used,waste of plating material (gold for instance) is avoided and theefficiency of the process is consequently improved.

In some embodiments, one might also use one or more of the features asdefined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will appear fromthe following description of three of its embodiments, provided asnon-limitative examples, and of the accompanying drawings.

On the drawings:

FIG. 1 is a partial planar view of a metallic strip,

FIG. 2 is a schematic partial perspective view of an apparatus accordingto a first embodiment,

FIGS. 3 a and 3 b are opposite exploded perspective views of a strip andbelt assembly for the apparatus of FIG. 2,

FIG. 4 is a view corresponding to FIG. 3 b, and not exploded, and

FIGS. 5 and 6 are views corresponding to FIG. 4 for a second andrespectively third embodiments. On the different figures, the samereference signs designate like or similar elements.

DETAILED DESCRIPTION

FIG. 1 schematically shows a pattern of an electrically conductive strip1. The strip 1 is formed as a repetition of a plurality of such patternsarranged the one after the others along the longitudinal direction X.The strip 1 may comprise hundreds of such patterns. The strip 1 is madefrom electrically conducting material, such as for example, a thin foilof copper which has been formed, for example stamped, as the shownshape. The strip is provided sufficiently thin and resilient to beflexible with respect to the X axis, so as to be provided as a reel ofmaterial. The strip 1 comprises a carrier band 2 which carrieselectrical leads 3. The carrier band 2 may define a plurality of windows4, each window enclosing a set of leads 3 which will form electricalterminals of a same electrical connector. The carrier band 2 comprises atop band 5 and a parallel bottom band 6 which extend along the directionX. The top and bottom bands 5, 6 are linked together by a structure 7,which ensures the mechanical stability of the carrier band 2. Forexample, the structure 7 comprises a plurality of parallel pillars 8extending along the transverse direction Y between the top 5 and bottombands 6. In this particular example, a window 4 is defined between twosubsequent pillars 8, and between the top and bottom bands 5, 6. Theleads 3 are made integral with the carrier band 2 using a linking bar 9which is a bar integral with the structure 7, as well as integral withany of the leads 3.

In the present example, the leads 3 extend sensibly straight along thedirection Y. However, other geometries are possible. Each lead 3 extendsbetween a first end 3 a and a second end 3 b, which are provided onopposite sides with respect to the bar 9. The first 3 a and second 3 bends are form tips which are more or less sharp depending on theapplication. All leads need not to have the same geometry. Some of theleads are longer than the others.

The carrier band 2 comprises a plurality of driving features 10. Suchfeatures 10 are for example holes 11 provided in the top and bottombands 5 and 6 in equidistant fashion along the direction X, so as tocooperate with a driving device, not shown, such as motor-driven toothedwheels having teeth designed to engage the holes 11.

Referring to FIG. 2, an apparatus 12 is described. The apparatus 12comprises at least one electroplating cell or tank 13 as well as afeeding reel 14 and an uptake reel 15. The feeding reel 14 feeds thestrip 1 to the electroplating cell 13. The strip is shown plain so as tosimplify the drawing, but is has windows as shown on FIG. 1. In theelectroplating cell 13, an electrically conductive material, inparticular metal, is electroplated on the strip 1. The apparatus 12 maycomprise one or more such cells 13 provided the one after the others, soas to apply a plurality of identical or different treatments to thestrip 1. The strip 1 is then wound again on the uptake reel 15.

The cell 13 encloses a solution bath 16 which is a liquid in which ametal to be deposited on a strip 1 is diluted. The cell 13 furthercomprises an electrode 17 to which an electrical potential can beapplied by a generator. The strip 1 is held at another potential so thatthe potential difference between the electrode 17 and the strip 1 causesmetal of the bath 16 to plate the strip 1.

In the cell 13, the strip 1 is assembled with a masking belt 18, whichmasks portions of the strip 1 on which electroplating is not desired. Adriving device 19, such as a roller, is rotated and used to drive thebelt 18 in the cell 13.

In the cell 13, the strip 1 and the belt 18 are pressed against eachother so that only the unmasked parts of the strip are plated with thediluted metal. In the shown embodiment, the strip 1 is held between twobelt portions 20 and 21. The belt portion 20 is a continuous belt indirect contact with the driving device 19 and also with one or moreadditional rollers 22.

Two rollers 23 a and 23 b apply the strip 1 directly against the beltportion 20 within the cell 13. These rollers may be provided outside thecell 3 and/or used to apply an electrical potential to the strip. Theyengage the holes 11 to drive the strip 1.

The second belt portion 21 is applied directly on the strip 1 usingrollers 24 a and 24 b. The second belt portion 21 may also be providedcontinuous (endless) using other rollers (not shown).

FIGS. 3 a and 3 b schematically show the way the strip 1 is held betweenthe two belt portions 20 and 21 in the bath. FIGS. 3 a and 3 b areschematically shown with the straight strip 1 and the belt portions 20and 21, but in fact they are wrapped around the driving device 19 asshown on FIG. 2.

The belt portion 20 has a face 26 which faces the strip 1 and anopposite face 27 which is driven by the driving device 19. For example,the face 27 has corrugations 28 which cooperate with complementaryfeatures of the driving device 19 so as to precisely drive the beltportion 20.

The belt 18 has a top band 29 which faces the top band 5 of the strip 1.The belt 18 also has a bottom band 30 which faces the bottom band 6 ofthe strip 1.

Furthermore, the belt 18 is provided with periodic structures 31, thegeometry of which mimics the geometry of the structures 7 of the strip1. In the present example, where the strip 1 has pillars 8, the belt 18is also provided with pillars.

In the present case, windows 32 are provided in the belt 18, whichcorrespond to the windows 4 of the strip 1. A recess or groove 33 isprovided on the inner face of one or more of the belt portions 20, 21,it is sufficiently large and deep for receiving the strip 1.

The belt portions 20 and 21 are also provided with inter-digitalfeatures, in order to precisely define their relative positions, inparticular with respect to the longitudinal direction X. Indeed, anyslippage or differential movement of the belts along the direction X,and any offset between the structures of the belt and the strip ought tobe avoided. For example, the belt portion 20 is provided with fingers 34which cooperate with complementary holes or recesses 35 of the beltportion 21 so as to precisely define the position of the two beltportions relative to one another.

The belt 18 is provided in a material which is sufficiently strong towithstand the driving by the driving device 19, which can carry thestrip without any slippage, and which can also seal efficiently the partof the structures which should not be electroplated, in particular in abath which is agitated in particular by the movement of the movingparts. For example, the belt portions are made from a reinforced aramideovercoated with a silicone coating adapted to provide the sealingability.

FIG. 4 shows the strip 1 and belt 18 assembly, the strip 1 being maskedby the belt 18. In this way, metal is electroplated only on the terminalleads and the bar 9. For example, nickel is electroplated in thisembodiment. In a second embodiment, as shown on FIG. 5, which can bealternative to the embodiment of FIG. 4, or after it, in another cell,the belt 18 is provided with a different geometry, so that only part ofthe leads 3 is submitted to electroplating. In particular, in thisembodiment, only the bottom part of the pins, below the bar 9, issubmitted to electroplating, for example of tin.

In yet another embodiment, as shown on FIG. 6, which may be alternativeor following the embodiments of FIG. 4 or 5, only the top part of theleads are electroplated, for example by gold, by masking the bottom partof the leads 3 with the masking belt 18.

The manufactured leads can then be processed for the manufacture ofelectrical connectors, for example by overmolding the leads in plasticand separating away the metallic frame.

1. A method for plating of strips comprising: providing a strip ofmaterial, providing a masking belt comprising patterned windows,providing a tank with a plating solution, generating a continuousmovement in the cell of an assembly of the strip and masking belt,whereby the structure of the masking belt masks portions of the strip inthe tank.
 2. Method according to claim 1, in which the belt comprises afirst and a second belt portions, each one of which masking a respectiveface of the strip.
 3. Method according to claim 2, wherein the first andsecond belt portions are provided with inter-digital features, so thatthe movement applied to the belt is transferred to the strip, andapplying the continuous movement to the belt.
 4. Method according toclaim 1, wherein the tank is an electroplating cell comprising anelectrode, the plating solution is an electroplating solution comprisingan electrical conductor, the method comprising electroplating theelectrical conductor on the metallic strip in the solution by applyingan electrical field between the strip and the electrode during thecontinuous movement.
 5. Method according to claim 1, comprisingproviding a metallic strip comprising a top band, a bottom band, astructure joining together the top and bottom bands, and leads disposedbetween the top band and the bottom band, the leads being designed toform electrical terminals of electrical connectors, providing maskingbelt portions comprising a top band, a bottom band, a structure joiningtogether the top and bottom bands, and wherein, in the tank, the topband of the masking belt masks the top band of the strip and the bottomband of the masking belt masks the bottom band of the strip.
 6. A methodfor the manufacture of electrical terminals for electrical connectors,wherein the method comprises: providing a metallic strip comprising atop band, a bottom band, a structure joining together the top and bottombands, and leads disposed between the top band and the bottom band, theleads designed to form electrical terminals of electrical connectors,providing a masking belt comprising a top band, a bottom band, astructure joining together the top and bottom bands, wherein the beltcomprises a first belt portion, a second belt portion, providing ametallisation cell having a chamber receiving a solution of anelectrical conductor, and an electrode, generating a continuous movementin the cell of an assembly of the metallic strip and masking belt,wherein the metallic strip is held between the first and second beltportions, and whereby the structure of the masking belt masks thestructure of the strip in the cell, electroplating the electricalconductor on the metallic strip in the solution by applying anelectrical field between the strip and the electrode during thecontinuous movement.
 7. Method according to claim 6, wherein each of thebelt portions comprises a top band, a bottom band, and a structurejoining together the top and bottom bands, wherein, in the cell: the topband of the first belt portion faces the top band of the second beltportion, the bottom band of the first belt portion faces the bottom bandof the second belt portion, the structure of the first belt portionfaces the structure of the second belt portion.
 8. An apparatus for theplating of strips, wherein the apparatus comprises: a feeding stationadapted to provide a strip, a masking belt comprising patterned windowsa tank for receiving a plating solution, a driver adapted to generate acontinuous movement in the tank of an assembly of the strip and maskingbelt, whereby the masking belt masks part of the strip in the tank. 9.An apparatus according to claim 8 further comprising a generator toapply an electrical field between the strip and an electrode placed inthe tank, during the continuous movement so as to electroplate anelectrical conductor on the strip in the solution